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Results for “Shaped Charges”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Redox oscillations in 18650-type lithium-ion cell revealed by in operando Compton scattering imaging

Compton scattering imaging using high-energy synchrotron x rays allows the visualization of the spatiotemporal lithiation state in lithium-ion batteries probed in operando. Here, we apply this imaging technique to the commercial 18650-type cylindrical lithium-ion battery. Our analysis of the line shapes of the Compton scattering spectra taken from different electrode layers reveals the emergence of inhomogeneous lithiation patterns during the charge-discharge cycles. Moreover, these patterns exhibit oscillations in time where the dominant period corresponds to the timescale of the charging curve.

42 ENGINEERING↗
DOE OSTI2020

Large Polarons as Key Quasiparticles in SrTiO 3 and SrTiO 3 -Based Heterostructures

Despite its simple structure and low degree of electronic correlation, SrTiO 3 (STO) features collective phenomena linked to charge transport and, ultimately, superconductivity, that are not yet fully explained. Thus, a better insight into the nature of the quasiparticles shaping the electronic and conduction properties of STO is needed. We studied the low-energy excitations of bulk STO and of the LaAlO 3 / SrTiO 3 two-dimensional electron gas (2DEG) by Ti L 3 edge resonant inelastic x-ray scattering. In all samples, we find the hallmark of polarons in the form of intense d d + phonon excitations, and a decrease of the LO3-mode electron-phonon coupling when going from insulating to highly conducting STO single crystals and heterostructures. Overall, both results are attributed to the dynamic screening of the large polaron self-induced polarization, showing that the low-temperature physics of STO and STO-based 2DEGs is dominated by large polaron quasiparticles.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Trapping Two Dissimilar Rigidity Ions with Identical Average Dynamics

It may seem obvious that ions with different charge-to-mass ratios (q/m) would have different dynamics in a trap or periodic focussing system, leading to different equilibrium bunch shapes and sizes. However, the ponderomotive acceleration in an oscillating field is proportional to (q/m) 2 rather than q/m for the direct field, leading to the possibility of combining the two effects to cancel any differences in the average dynamics between two chosen species.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Design and Manufacturing of High Performance, Reduced Charge Heat Exchangers

A framework of stress analysis and fatigue analysis was developed. Utilizing the framework, stress analysis and fatigue analysis of high-performance heat exchangers with non-round shaped tubes were studied. The tubes, headers and welding layers were studied separately before analyzing the assembled heat exchangers. Results reveal different stress strength on the different shapes of tubes and headers. Unevenly welding distribution is also discussed in the report. Moreover, the fatigue analysis results of the heat exchanger are helping to estimate the lifetime of the heat exchanger from fatigue point of view.

42 ENGINEERING↗
DOE OSTI2020

Fast-neutron response of LaBr 3 (Ce) and LaCl 3 (Ce) scintillators

The response of LaBr 3 (Ce) and LaCl 3 (Ce) scintillators to fast neutrons is investigated. Neutron-induced charged-particle reactions are observed in both materials when exposed to the fast neutrons produced by an AmBe source, with pulse-shape discrimination used to separate channels. LaBr 3 (Ce) is found to have the best separation between reaction channels, while LaCl 3 (Ce) has a significantly higher efficiency.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Efficient charge to spin conversion in iridium oxide thin films

Many 5d transition metal oxides have a unique electronic structure, where the density of states near the Fermi level is dominated by only 5d electrons with strong spin–orbit coupling. IrO 2 , a Dirac nodal line semi-metal, is the simplest of these oxides. The presence of 5d electrons and gap opening of Dirac nodal lines via strong spin–orbit coupling allows for the hybridization of the 5d electrons of the oxide with the itinerant d electrons of a ferromagnet, while simultaneously increasing the intrinsic spin Hall effect. We report large charge-to-spin conversion in thin films of this material using spin-torque ferromagnetic resonance experiments. Finally, by independently performing line shape analysis and linewidth modulation experiments, we conclusively determine the spin Hall angle of optimized IrO 2 films to be ∼8 times larger than that of Pt.

Ferromagnetic materials↗
DOE OSTI2024

Ultrafast laser triggered electron emission from ultrananocrystalline diamond pyramid tip cathode

Nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] pyramid tip cathode has been considered as a next-generation high peak current electron source for dielectric laser accelerators as well as other high peak current particle accelerator applications. In this work, we study non-linear photoemission from an (N)UNCD pyramid tip cathode using an ultrafast laser with the pulse length of 150 fs with the central wavelength of 800 nm in the peak intensity range of 10 9 –10 10 W/cm 2 . We demonstrated that as the incident laser intensity increases, the current emitted from the nano-tip first increases as a power function with an exponent of about 5 and then starts to roll over to an exponent of 3. This roll over is attributed to the Coulomb interaction between electrons emitted from the tip also known as the space charge. We also measured the photoemission electron energy spectra that show electrons with energies as high as ~10 eV. Based on the shape of the electron energy spectra, we conclude that the high-energy electrons are thermally emitted electrons due to ultrafast laser heating at the tip of the (N)UNCD pyramid tip cathode.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Design of a compact, cryogen-free superconducting solenoid for the electron lens of the Fermilab Integrable Optics Test Accelerator (IOTA)

The proposed electron lens for Fermilab's Integrable Optics Test Accelerator (IOTA) will broaden its capabilities by enabling new research in nonlinear integrable optics, space-charge compensation, proton beam cooling, and more. The electron lens is based on a 5–10 keV, 1–2 A electron beam, shaped using a 0.7 m long, 0.8 T solenoidal magnetic field. A cryogen-free superconducting solenoid has been designed to provide this solenoidal field, taking into consideration the constraints on space, utilities, and infrastructure in the IOTA experimental hall. The solenoid is made of copper stabilized niobium-titanium conductor, conduction-cooled using 4 K closed-cycle cryocoolers. This paper describes the overall design of the solenoid encompassing its mechanical construction, current leads optimization, cryogenic thermal modeling that provides estimates of cooldown time and static/dynamic heat loads, and quench analysis.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Transverse-momentum and event-shape dependence of D-meson flow harmonics in Pb–Pb collisions at s NN = 5.02 TeV

The elliptic and triangular flow coefficients v 2 and v 3 of prompt D 0 , D + , and D * + mesons were measured at midrapidity ( | y | < 0.8 ) in Pb–Pb collisions at the centre-of-mass energy per nucleon pair of s NN = 5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays in the transverse momentum interval 1 < p T < 36 GeV / c in central (0–10%) and semi-central (30–50%) collisions. Compared to pions, protons, and J / ψ mesons, the average D-meson v n harmonics are compatible within uncertainties with a mass hierarchy for p T ≲ 3 GeV / c , and are similar to those of charged pions for higher p T . The coupling of the charm quark to the light quarks in the underlying medium is further investigated with the application of the event-shape engineering (ESE) technique to the D-meson v 2 and p T -differential yields. The D-meson v 2 is correlated with average bulk elliptic flow in both central and semi-central collisions. Within the current precision, the ratios of per-event D-meson yields in the ESE-selected and unbiased samples are found to be compatible with unity. All the measurements are found to be reasonably well described by theoretical calculations including the effects of charm-quark transport and the recombination of charm quarks with light quarks in a hydrodynamically expanding medium.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Peak load reduction and load shaping in HVAC and refrigeration systems in commercial buildings by using a novel lightweight dynamic priority-based control strategy

Reducing peak power demand in a building can reduce electricity expenses for the building owner and contribute to the efficiency and reliability of the electrical power grid. For the building owner, reduced expenses come from the reduction or elimination of peak power charges on electricity bills. For the power system operator, reducing peak power demand leads to a more predictable load profile and reduces stress on the electric grid system. Herein we present a computationally inexpensive, dynamic, and retrofit-deployable control strategy to effect peak load reduction and load shaping. The effectiveness of the control strategy is examined in a simulation with 80 air-conditioning units and 40 refrigeration units. The results show that a peak demand reduction of 60 kW can be achieved relative to peak demand in a typical set point–based approach. The proposed strategy was deployed in a gymnasium building with four rooftop HVAC units, where it showed over 15% peak demand (kW) reduction savings while maintaining or lowering energy consumption (in kilowatt-hours) relative to the set point–based thermostat controls.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

Entropy and Seebeck signals meet on the edges

Here, we explore the electronic entropy per particle s and Seebeck coefficient S in zigzag graphene ribbons. Pristine and edge-doped ribbons are considered using tight-binding models to inspect the role of edge states in the observed thermal transport properties. As a band gap opens when the ribbons are doped at one or both edges, due to asymmetric edge potentials, we find that s and S signals are closely related to each other: both develop sharp dip-peak line shapes as the chemical potential lies in the gap, while the ratio s/S exhibits a near-constant value equal to the elementary charge e at low temperatures. This constant ratio suggests that S can be seen as the transport differential entropy per charge, as suggested by some authors. Our calculations also indicate that measurement of s and S may be useful as a spectroscopic probe of different electronic energy scales involved in such quantities in gapped materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Reaction plane correlated triangular flow in Au + Au collisions at $\sqrt{s_{NN}}$ = 3 GeV

Here, we measure triangular flow relative to the reaction plane at 3 GeV center-of-mass energy in Au + Au collisions at the BNL Relativistic Heavy Ion Collider. A significant v 3 signal for protons is observed, which increases for higher rapidity, higher transverse momentum, and more peripheral collisions. The triangular flow is essentially rapidity-odd with a slope at midrapidity, dv 3 /dy| (y=0) , opposite in sign compared to the slope for directed flow. No significant v 3 signal is observed for charged pions and kaons. Comparisons with models suggest that a mean field potential is required to describe these results, and that the triangular shape of the participant nucleons is the result of stopping and nuclear geometry.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Raman gain control in optical fibers with orbital-angular-momentum-induced chirality of light

Stimulated Raman scattering is a particularly robust nonlinearity, occurring in virtually every material because its spectral linewidth and associated frequency shift do not typically depend on phases or directions (i.e. wavevectors) of the interacting light beams. In amorphous materials such as glass fibers, Raman bandwidths are large, enabling its use as a broadband gain element. This ubiquity makes it a versatile means for achieving optical amplification or realizing lasers over a large range of pulsewidths at user-defined colors. However, this ease of deploying the effect also presents itself as a stubborn source of noise in fiber-based quantum sources or parasitic emission in fiber lasers. Here, we show that orbital angular momentum carrying light beams experiencing spin-orbit interactions yield novel phase-matching criteria for Raman scattering. This enables tailoring its spectral shape (by over half the Raman shift in a given material) as well as strength (by ∼ 100×) simply by controlling light’s topological charge – a capability of utility across the multitude of applications where modulating Raman scattering is desired.

Liu, Xiao (ORCID:000000032239762X)↗
DOE OSTI2024

Correlation of Dimer-Linker-Induced Conformational Lock with Nonradiative Energy Loss in Organic Solar Cells

The efficiencies of dimer-based devices still lag those of their small molecule-based counterparts. This is primarily due to the considerable dihedrals in the dimer skeleton, which compromises the molecular packing, thus influencing the charge generation and nonradiative voltage loss (ΔV oc,nr ). Herein, we developed two dimeric acceptors with varied π-linkers to investigate the influence of linker-induced conformational lock on ΔV oc,nr . We find that the helically lapped O-shaped dimer delivers better intermolecular packing than the planar S-shaped one that incorporates a bulkier π-linker. However, its planar skeleton is instead more favorable for forming a compact and ordered stacking with the host acceptor in ternary blend. This possibly promotes exciton dissociation, thus reducing the nonradiative decay of excited states. Moreover, its longer exciton lifetime could offer additional charge-transfer channels. Finally, these contributions effectively minimize ΔV oc,nr to 0.195 eV, while delivering a high efficiency approaching 20% in the derived ternary device.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Investigation of ASIC-based signal readout electronics for LEGEND-1000

LEGEND, the Large Enriched Germanium Experiment for Neutrinoless ββ Decay, is a ton-scale experimental program to search for neutrinoless double beta (0νββ) decay in the isotope 76 Ge with an unprecedented sensitivity. Building on the success of the low-background 76 Ge-based GERDA and Majorana Demonstrator experiments, the LEGEND collaboration is targeting a signal discovery sensitivity beyond 10 28 yr on the decay half-life with approximately 10 t∙yr of exposure. Signal readout electronics in close proximity to the detectors plays a major role in maximizing the experiment's discovery sensitivity by reducing electronic noise and improving pulse shape analysis capabilities for the rejection of backgrounds. However, the proximity also poses unique challenges for the radiopurity of the electronics. Application-specific integrated circuit (ASIC) technology allows the implementation of the entire charge sensitive amplifier (CSA) into a single low-mass chip while improving the electronic noise and reducing the power consumption. In this work, we investigated the properties and electronic performance of a commercially available ASIC CSA, the XGLab CUBE preamplifier, together with a p-type point contact high-purity germanium detector. We show that low noise levels and excellent energy resolutions can be obtained with this readout. Moreover, we demonstrate the viability of pulse shape discrimination techniques for reducing background events.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Start-to-End Simulation of the Drive-Beam Longitudinal Dynamics for Beam-Driven Wakefield Acceleration

Collinear beam-driven wakefield acceleration (WFA) relies on shaped driver beam to provide higher accelerating gradient at a smaller cost and physical footprint. This acceleration scheme is currently envisioned to accelerate electron beams capable of driving free-electron laser *. Start-to-end simulation of drive-bunch beam dynamics is crucial for the evaluation of the design of accelerators built upon WFA. We report the start-to-end longitudinal beam dynamics simulations of an accelerator beamline capable of producing high charge drive beam. The generated wakefield when it passes through a corrugated waveguide results in a transformer ratio of 5. This paper especially discusses the challenges and criteria associated with the generation of temporally-shaped driver beam, including the beam formation in the photoinjector, and the influence of energy chirp control on beam transport stability.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

In Situ Measurement of Adhesion for Multimetallic Nanoparticles

The adhesion of nanoparticles to their supports is key to their performance and stability. However, scientific advances in this area have been hampered by the difficulty of experimentally probing adhesion. To date, only a single technique has been developed that can directly measure nanoparticle adhesion, and this technique is inherently limited to monometallic systems. We present a versatile technique for the direct measurement of adhesion for bimetallic nanoparticle systems. This technique combines the spatial resolution of transmission electron microscopy with the force resolution of an atomic force microscope to probe individual, well-characterized nanoparticles. A first study of supported bimetallic nanoparticles provides new insights into the complex impact of alloying on nanoparticle adhesion, explained by charge transfer between constituent metals. The new experimental technique is readily extensible to study other multimetallic nanoparticle systems, including the effects of particle size, shape, and orientation, thus enabling advances in our understanding of nanoparticle physics.

36 MATERIALS SCIENCE↗